Delta
Topic: Landforms and their Evolution: Rivers, Groundwater, Glaciers, Waves and Wind · NCERT: Class 7, Ch 1 "Geographical Diversity of India"; Class 9, Ch 2 "Shaping of the Earth's Surface"; Class 11, Ch 2 "Structure and Physiography"; Class 11, Ch 3 "Drainage System"; Class 11, Ch 6 "Landforms and their Evolution"
Meaning
A delta is a low, flat plain made of sediment at the mouth of a river. It forms where the river drops its load faster than waves and tides can carry it away. The river slows down on reaching the sea. Coarse material settles first and finer material settles further out, so delta deposits are well sorted and stratified (laid down in layers). Distributaries spread the sediment across the delta. Deltas are fertile and densely settled.
Example
The Ganga-Brahmaputra delta (the Sundarbans) in West Bengal and Bangladesh is the largest delta in the world. In the Peninsula, the east-flowing Mahanadi, Godavari, Krishna and Kaveri also build deltas.
Don't confuse with
- Estuary: an estuary is a funnel-shaped tidal mouth where tides carry sediment out to sea, so no delta builds up. The Narmada and Tapi form estuaries.
- Alluvial fan: a fan forms at the foot of a mountain and is made of coarse, unsorted material.
Related concepts
- Alluvial fan
- Distributary
- Estuary
- Floodplain
- Natural levee
- Point bar
- Meander
- Slip-off slope and undercut bank
- Oxbow lake
- Braided channel